Enar's Embassy is not bad. It's a great wonder on its own. The Scouts Tavern sounds great too with reduced scout times+extra goodie boxes. The fact that one helps the other is just a bonus.
I can understand why an advanced chapter player would hesitate to build Enars at that late point in the game.
I'm not an advanced chapter player. I'm looking at building Enar's in chapter 9 and leveling it as soon as possible. At level 30, the Enars Embassy ancient wonder power is 400. These numbers are based on scouting and completing the bare minimum of provinces required to move forward in chapters.
completed provinces x AW power = mana per scout.
Ch9. 30 scouts=2,280,000 mana.
Ch10 30 scouts=2,640,000 mana.
Ch11 30 scouts=3,000,000 mana
Ch12 40 scouts=4,480,000 mana
Ch13 40 scouts=5,120,000 mana
Ch14 40 scouts=5,760,000 mana
Ch15 40 scouts=6,400,000 mana
Ch16 40 scouts=7,040.000 mana
Ch17 40 scouts=7,680,000 mana
Ch18 40 scouts=8,320,000 mana
Ch19 40 scouts= 8,960,000 mana
Ch20 40 scouts= 9,600,000 mana
Total Mana=71,280,000
This doesn't have to be everyone's favorite mana producer but I do think players should give it a look instead of writing it off because someone else said so. I'm going to scout anyway, I might as well get paid.